The 450-kilometre (280-mile) coastline, which is lapped by the Adriatic and Ionian seas, was off-limits under the communist regime which ruled the Balkan state until 1990, with orders to shoot anyone caught diving without authorisation.

The 10 communities have at least 2,000 residents, but each community will decide if they evacuate or not. Antigua al Rescate, an organization that helped communities after a devastating eruption in June, and a newspaper in the capital reported at least three communities were doing so.

The number of people missing or unaccounted for in Butte County was 1,202 as of Sunday, though those figures may continue to fluctuate as authorities track down the names on the list, according to Butte County Sheriff Kory Honea.

In her first interview since the story was published, Sandberg told "CBS This Morning" co-host Norah O'Donnell she did not know about an effort described by the Times to publish stories critical of other tech companies, an apparent attempt to deflect attention away from Facebook.